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1907] HOLM— VEGETATIVE ORGANS OF RHEXIA 23 



yet been thoroughly investigated. The monograph contributed by 

 CoGNiAuxs is purely systematic and adds nothing to the natural 

 history of these interesting plants. Copious as is the literature, very 

 little attention has been paid to the following questions: how the 

 plants grow, how they develop from seeds to mature plants, and 

 how well the structural characteristics are preserved under various 

 conditions. 



most widely distributed in America, very 



north 



that occurs in the United States and Canada, with about ten species. 

 Two of these, R. virginica and R. mariana, occur in the District of 

 Columbia, the former extending as far north as Ontario, the latter 

 to New Jersey. They both inhabit sandy swamps, associated with 

 Lilium superbum, certain Cyperaceae (Scleria, Fimbristylis, Scirpus, 

 and Carex), Polygalaceae, Violaceae, etc. 



Having had the opportunity of studying these two species in the 

 field at various seasons, I have found several points in their external 



F 



Structure which have not hitherto been described, and which may serve 



as a small contribution to the knowledge of the life-history of these 



I interesting plants. To this is added a brief anatomical description 



of the vegetative organs, and especially of the roots, since these have 

 not been studied heretofore. 



1 .' 



Rhexia virginica L. 



■f 



While studying the vegetative propagation exhibited by representa- 

 tives of the local flora, I never was able to find any specimen of this 

 species with a rhizome as described in the various manuals. Accord- 

 ing to Britton, "Gray, and Small, this species should possess "hori- 

 zontal, slender, and tuberiferous rootstocks." That this statement 

 is very incorrect may be seen from the following notes, in which I 

 shall endeavor to show that the underground organs described as 

 tuberiferous rootstocks are simply tuberous roots; and that the devel- 

 opment of root-shoots is of great importance to the plant, being its 

 only means of vegetative propagation. 



Root-shoots of adult specimens, like those of figs. 3 and 4, do not - 

 give any clear idea of the remarkable way in which this herbaceous 



5 DeCandolle's Monogr. phan€rog. 7:385. 1891. 



